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Slowly Changing Dimensions (SCDs) Flashcards

7 cards from real Data Engineering practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. When loading a Type 2 dimension, a record's tracked attribute changes. What is the correct sequence?

    Answer: Expire the current row, then insert a new row marked current

    You close the existing version (set end_date, is_current=false) and insert a fresh current row.

  2. Which technique efficiently detects whether any tracked column changed during a Type 2 load?

    Answer: Comparing a hash of the tracked columns

    Hashing the tracked columns lets a single comparison detect any change quickly.

  3. A late-arriving dimension means a fact references a dimension member that:

    Answer: Does not yet exist in the dimension when the fact loads

    Late-arriving dimensions require inserting a placeholder member so the fact can be loaded.

  4. How is a high-end_date often represented for the current Type 2 row?

    Answer: A far-future sentinel date like 9999-12-31

    A far-future sentinel keeps BETWEEN range queries simple while marking the row as open.

  5. What problem can occur if a non-tracked attribute is mistakenly configured as Type 2?

    Answer: Unnecessary version explosion bloating the dimension

    Treating volatile non-essential columns as Type 2 creates many rows and inflates storage.

  6. In a hybrid Type 6 SCD, which behaviors are combined?

    Answer: Type 1, 2, and 3 (1+2+3=6) in one dimension

    Type 6 blends overwrite, new-row history, and a current-value column for flexible reporting.

  7. A mini-dimension is commonly used to:

    Answer: Pull rapidly changing attributes out of a large dimension

    Mini-dimensions isolate fast-changing attributes to prevent version explosion in the main dimension.